1. Field of the Invention
This invention relates to the making of polyether polyol compositions, and in particular, to the making of such compositions which are highly branched and have a relatively high molecular weight, such as approximately 12,000 or greater. Still more particularly, it relates to derivatives of polyglycerol having a highly branched structure and high molecular weight.
2. Description of the Prior Art
It may be taken as known, for example, from U.S. Pat. No. 3,636,774, that glycerol may be polymerized to form polyglycerol. It is known, for example, from U.S. Pat. No. 3,932,532, that the active hydrogen atoms of polyglycerol can be reacted with alkylene oxides to form polyglycerol ethers. Moreover, those skilled in the art will appreciate that it is possible to add several mols of ethylene oxide or propylene oxide per active OH group present in the polyglycerol. The addition of one mol of ethylene oxide or propylene oxide at one of the hydroxyl groups of the polyglycerol leaves an oxyethylene or oxypropylene group attached to the polyglycerol, to form a polyglycerol ether, but the added group itself terminates in an active hydrogen atom, which is capable of reacting with additional ethylene oxide or propylene oxide.
It has been found, however, that there are limits to the extent to which ethylene and/or propylene oxide may be added to, for example, a polyglycerol of 5 to 30 glycerol units. The reaction of a material which contains an active hydrogen atom with ethylene oxide to produce an oxyethylated material of high molecular weight usually proceeds quite smoothly under proper conditions of catalysis, temperature, and pressure and with adequate mixing, but there is a problem in the oxyethylation of a polyglycerol of 6 to 30 glycerol units, namely, that it is not convenient to attempt to produce from the polyglycerol in one step or stage a highly oxyethylated product; materials of relatively high molecular weight are involved, and it is difficult to ensure that the relatively minor proportion of polyglycerol material is adequately stirred into and properly mixed and reacted with the ethylene oxide. Better results are obtained, without the use of an autoclave of relatively great size, if the reaction is conducted in a number of steps or stages, such as 2 to 4, with the polyglycerol or alkoxylated polyglycerol being in each stage reacted with about 4 to 10 times as much by weight of ethylene oxide. Even for the further consideration discussed below, the use of propylene oxide in place of ethylene oxide raises just the same problems.
Still another consideration is that with long chains of oxypropylene units, there is the additional possibility of obtaining a "transfer" reaction in place of the desired chain-growing or "propagation" reaction. The "transfer" reaction creates an allyl-alcohol entity which is relatively more reactive than the polymer, and it or oxypropylated polymers derived from it, compete with increasing success for the available unreacted propylene oxide. See, for example, "Polyethers" by C. C. Price, Accounts of Chemical Research, Vol. 7, p. 294 at 295 (1974).
It may also be taken as known that a material containing an active OH group will react with a benzene sulfonyl ester or toluene sulfonyl ester to form a coupled compound, with the benzene sulfonate or toluene sulfonate serving as a "leaving group". For example, it is known from an article of Z. Foldi, Berichte, Vol. 53, 1839 et seq. (1920), that for the alkylation of phenols, esters of benzenesulfonic acid may be used. It is also true that the benzenesulfonic acid diester of ethylene glycol is known as a compound, for example, from an article by Foldi in Berichte, Vol. 60, p. 660 (1927). It has not, however, been obvious to those of ordinary skill in the art that the latter compound can be brought into reactive relationship with an oxyalkylated polyglycerol compound, serving to convert it to a coupled, highly branched, nonionic product of high molecular weight, a material suited for uses that the materials of lower molecular weight, made merely by the oxyalkylation of polyglycerol, serve less adequately or not at all.